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Abstract:

In order to increase the continuous operating time of a display device
driven by a battery or the like, and a portable information terminal
using the same, the volume and weight of the battery are increased. Thus,
there arises a trade-off between the increased capacity of the battery
and the portability of the device/terminal. Therefore, the invention
provides a display device with portability ensured, which is capable of
operating continuously for long periods and a portable information
terminal using the same. In the display device, TFTs and an RFID tag are
formed over the same insulating substrate. The RFID tag detects signals
from a reader/writer, and generates DC power based on the signals. While
the RFID tag is detecting signals, the display device is driven by the DC
power generated in the RFID tag.

Claims:

1. A receiver comprising: a device a battery configured to supply
electrical power to the device; an antenna; a power source circuit
configured to generate electrical power from a signal received by the
antenna; and a selector circuit configured to electrically connect one of
the battery and the power source circuit to the device, wherein the
receiver is provided with an identification number that can be read out
by a reader/writer.

2. The receiver according to claim 1, wherein an RFID tag comprised in
the receiver is assigned with the identification number.

3. The receiver according to claim 1, wherein the antenna is constructed
of a resonant circuit comprising a coil and a capacitor connected in
parallel; wherein the selector circuit is configured to electrically
connect the device to the power source circuit when the resonant circuit
is in a resonant state.

4. The receiver according to claim 1, wherein the device is a display
device.

5. The receiver according to claim 1, wherein the antenna is constructed
of a resonant circuit comprising a coil and a capacitor connected in
parallel; wherein the coil, the capacitor, the power source circuit and
the selector circuit are included in the RFID tag.

6. The receiver according to claim 1, wherein the receiver is configured
to receive data from a portable terminal.

7. The receiver according to claim 1, wherein the battery is configured
to output a first direct current power; and wherein the power source
circuit is configured to output a second direct current power.

8. A receiver comprising: a device; a battery configured to supply
electrical power to the device; an antenna; a power source circuit
configured to generate electrical power from a signal received by the
antenna; and a selector circuit configured to electrically connect one of
the battery and the power source circuit to the device, wherein the
receiver is provided with an identification number that can be read out
by a reader/writer; and wherein the receiver is configured to receive
data in accordance with the identification number.

9. The receiver according to claim 8, wherein an RFID tag comprised in
the receiver is assigned with the identification number.

10. The receiver according to claim 8, wherein the antenna is constructed
of a resonant circuit comprising a coil and a capacitor connected in
parallel; wherein the selector circuit is configured to electrically
connect the device to the power source circuit when the resonant circuit
is in a resonant state.

11. The receiver according to claim 8, wherein the device is a display
device.

12. The receiver according to claim 8, wherein the antenna is constructed
of a resonant circuit comprising a coil and a capacitor connected in
parallel; wherein the coil, the capacitor, the power source circuit and
the selector circuit are included in the RFID tag.

13. The receiver according to claim 8, wherein the receiver is configured
to receive data from a portable terminal.

14. The receiver according to claim 8, wherein the battery is configured
to output a first direct current power; and wherein the power source
circuit is configured to output a second direct current power.

15. A receiver comprising: a device; a battery configured to supply
electrical power to the device; an antenna; a power source circuit
configured to generate electrical power from a signal received by the
antenna; and a selector circuit configured to electrically connect one of
the battery and the power source circuit to the device, wherein the
receiver is provided with an identification number that be sent to
reader/writer; and wherein the receiver is configured to receive data in
accordance with the identification number.

16. The receiver according to claim 15, wherein an RFID tag comprised in
the receiver is assigned with the identification number.

17. The receiver according to claim 15, wherein the antenna is
constructed of a resonant circuit comprising a coil and a capacitor
connected in parallel; wherein the selector circuit is configured to
electrically connect the device to the power source circuit when the
resonant circuit is in a resonant state.

18. The receiver according to claim 15, wherein the device is a display
device.

19. The receiver according to claim 15, wherein the antenna is
constructed of a resonant circuit comprising a coil and a capacitor
connected in parallel; wherein the coil, the capacitor, the power source
circuit and the selector circuit are included in the RFID tag.

20. The receiver according to claim 15, wherein the receiver is
configured to receive data from a portable terminal.

21. The receiver according to claim 15, wherein the battery is configured
to output a first direct current power; and wherein the power source
circuit is configured to output a second direct current power.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a display device and a portable
terminal. In particular, the invention relates to a portable terminal
having a display device in which images are displayed by controlling
multiple pixels arranged in matrix. More particularly, the invention
relates to a portable terminal having a flat-panel display device in
which images are displayed by using multiple thin film transistors
provided over an insulating substrate.

[0003] 2. Description of the Related Art

[0004] In recent years, RFID (Radio Frequency IDentification) tags have
been researched and developed as a new technology for goods
identification and management in the distribution industry as an
alternative to conventional barcodes, and also examined as a new personal
identification means. Further, it is drawing attentions as a fundamental
technology for advancing IT and automation of the infrastructure (cf.
Japanese Patent Publication No. Sho62-43238). RFID tags are also called
RF chips, RF tags, IC (Integrated Circuit) chips, IC tags, wireless
chips, wireless tags, electronic chips, electronic tags, wireless
processors, wireless memories and the like.

[0005] RFID tags have various advantages in that wireless communication
with a reader/writer is enabled by providing an antenna in an IC chip
used as the tag, and multiple objects can be concurrently identified
unlike a barcode as a typical conventional identification means that
requires objects to be directly read out with a scanning barcode reader
one by one.

[0006] Further, there is an RFID tag that has no internal power source but
has an antenna portion for detecting electromagnetic waves transmitted
from a reader/writer, based on which direct current (hereinafter referred
to as DC) power is generated to operate the RFID tag.

[0007] Portable terminals such as a portable phone or a PDA (Personal
Digital Assistant) are required to be further reduced in weight and size
for improving the convenience. Therefore, each component of the portable
terminals is required to be further reduced in volume. For a display
device to be an interface portion, a flat panel display is mainly adopted
where circuits are configured with multiple thin film transistors (TFTs)
provided over an insulating substrate formed of glass, plastic or the
like.

[0008] Further, in accordance with the improved performance of portable
terminals per se, possibility of users carrying the portable terminals
has been expanding, and thus a longer continuous operating time is
required as compared to the conventional ones.

[0009] In order to increase the continuous operating time of portable
terminals, each component of the portable terminals is required to be
reduced in power consumption, and a battery is required to be increased
in capacity. In order to achieve the former requirement for the longer
continuous operating time, various measures have already been taken such
as lowering the driving voltage or controlling the portable terminals to
enter a standby mode often by software control with an aim to reduce
power consumption. However, as for the later requirement for the
increased capacity of the battery, the volume of the battery is increased
if the capacity of the battery is increased; therefore, there arises a
trade-off between the increased capacity of the battery and the
aforementioned reduction in size and weight.

SUMMARY OF THE INVENTION

[0010] In view of the foregoing problems, it is an object of the invention
to provide a portable terminal with an increased continuous operating
time. It is another object of the invention to provide a portable
terminal with an improved continuous operating time along with reduction
in size and weight.

[0011] In the invention, functional units of an RFID are formed by using
TFTs over the same insulating substrate as, and concurrently with a step
of forming TFTs that constitute a driver circuit of a display device.
Here, the TFTs for constructing the display device and the TFTs for
constructing the RFID tag may have basically the same structures, and
thus manufacturing steps thereof can be simplified.

[0012] When the RFID tag that is incorporated in the display device is put
close to a reader/writer, an antenna in the RFID tag detects signals from
the reader/writer. Then, a power source circuit included in the
functional unit of the RFID tag generates DC power based on the signals
detected from the reader/writer. The generated DC power is used for
driving the display device.

[0013] Power supply to the display device may be carried out by any of the
following methods: a method for supplying power from a home power source
or the like through an AC (Alternating Current) adapter or the like; a
method for supplying power from a built-in battery; a method for
supplying power that is generated by the RFID tag; or the like. When the
RFID is activated by detecting signals from the reader/writer, the RFID
tag generates a signal for switching a power source, thereby power supply
to the display device is switched from the AC adapter or the battery to
the power source circuit in the RFID tag. When the RFID tag is moved away
from a region where the RFID can detect signals from the reader/writer,
the power supply is switched again from the internal power source circuit
to the AC adapter or the battery.

[0014] Note that switching of the power supply as for the case of
supplying power from a home power source or the like through an AC
adapter or the like, and the case of supplying power from a built-in
battery has already been carried out in many portable terminals;
therefore, the method is not described here. Thus, the switching may be
carried out appropriately in accordance with the conventional method.

[0015] A portable terminal of the invention includes a resonant circuit
having a coil and a capacitor connected in parallel, a power source
circuit for generating DC power by rectifying AC power that is induced by
bringing the resonant circuit into a resonant state. Thus, the DC power
generated in the power source circuit is used for driving the portable
terminal.

[0016] A display device of the invention displays images by controlling
multiple pixels arranged in matrix. The display device includes a
resonant circuit having a coil and a capacitor connected in parallel, a
power source circuit for generating DC power by rectifying AC power that
is induced by bringing the resonant circuit into a resonant state. The DC
power generated in the power source circuit is used for driving a part of
or the entire circuits that constitute the display device.

[0017] A portable terminal of the invention includes a display device in
which images are displayed by controlling multiple pixels arranged in
matrix, and a battery for supplying a first DC power. The display device
includes a resonant circuit having a coil and a capacitor connected in
parallel, and a power source circuit for generating a second DC power by
rectifying AC power that is induced by bringing the resonant circuit into
a resonant state. The first DC power or the second DC power is used for
driving a part of or the entire circuits that constitute the display
device.

[0018] In the portable terminal of the invention with the aforementioned
configuration, the display device further includes a selector circuit for
selecting the first DC power or the second DC power. The selector circuit
selects the first DC power when the resonant circuit is not in the
resonant state whereas it selects the second DC power when the resonant
circuit is in the resonant state.

[0019] In the invention, the display device further includes a source
driver and a gate driver for controlling the multiple pixels.

[0020] In the invention, the multiple pixels, the resonant circuit and the
power source circuit are formed over the same insulating substrate.

[0021] In the invention, the multiple pixels, the resonant circuit, the
power source circuit and the selector circuit are formed over the same
insulating substrate.

[0022] In the invention, the multiple pixels, the resonant circuit, the
power source circuit, the selector circuit, the source driver and the
gate driver are formed over the same insulating substrate.

[0023] In the invention, the multiple pixels and the power source circuit
include thin film transistors provided over an insulating substrate
formed of glass or plastic.

[0024] In the invention, the multiple pixels, the power source circuit and
the selector circuit include thin film transistors provided over an
insulating substrate formed of glass or plastic.

[0025] In the invention, the multiple pixels, the power source circuit,
the selector circuit, the source driver and the gate driver include thin
film transistors provided over an insulating substrate formed of glass or
plastic.

[0026] In the invention, each of the multiple pixels includes a liquid
crystal element or a self-luminous element.

[0027] Conventionally, portable terminals have been operated by using only
a battery with limited capacity when the terminals are carried about.
However, in the invention, power supply at an arbitrary place can be
enabled within such a range that signals from a reader/writer of an RFID
tag can be detected, thereby the operating time of the portable terminals
can be increased.

[0028] In addition, the main feature of the invention is the power supply
to the display device, switching operation of the power supply and the
like. That is, unlike a general RFID tag that communicates signals with
only registered readers/writers, the invention enables signals outputted
from unspecified readers/writers to be detected by the RFID tag, based on
which the RFID can generate power. Thus, the RFID tag of the invention
can be used in various institutions. Needless to say, identification of
the terminal or the like can be carried out in parallel with the function
described in this specification.

[0029] Further, by forming the pixel portion for displaying images and the
RFID tag over the same substrate, the number of components can be
reduced, thereby the portable terminal can be reduced in size and weight.

[0034] FIGS. 4A and 4B illustrate one embodiment of the invention; and

[0035] FIGS. 5A to 5C illustrate one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0036] Description is made with reference to FIG. 1 on one embodiment mode
of the invention. A portable terminal 101 has a display device 102 and a
battery 111 as main components. The display device 102 has a display
portion 103a and an RFID tag 103b. The RFID tag 103b has a power source
circuit 105, a functional unit 106 (including a selector circuit), and an
antenna constructed of a resonant circuit that includes a coil 107 and a
capacitor 108 connected in parallel. Here, the functional unit 106
includes a memory in which identification data is stored, a logic circuit
for performing arithmetic operation such as generation of signals to be
outputted to an antenna of a reader/writer, and the like. In addition,
the display device includes switches 109 and 110 for selecting one of the
power source circuit 105 or the battery 111 to supply power sources VDD
and VSS (potential values are not specified; VSS is a ground potential,
for example) for driving the display portion 103a. The switches 109 and
110 are controlled by the selector circuit included in the functional
unit 106. Each of the switches 109 and 110 selects one of the power
source circuit 105 or the battery 111 to supply the power sources VDD and
VSS for driving the display portion 103a. Reference numeral 104 is an
antenna provided at a reader/writer side.

[0037] Although the configuration of the switches 109 and 110 is not
specifically limited, each of the switches herein has two input
terminals, an output terminal and a control terminal, and a signal from
the selector circuit included in the functional unit 106 is inputted to
the control terminal to select one of the two input terminals, thereby
the selected input terminal is short-circuited to the output terminal.

[0038] When the display device 102 having the RFID tag 103b enters a
region 201 where a signal 120 from the antenna 104 of the reader/writer
side can be detected (which corresponds to a region shown by the slant
bars in FIG. 2A), the parallel resonant circuit in which the coil 107 and
the capacitor 108 are connected in parallel is brought into a resonant
state, thereby AC power is induced between opposite ends of the parallel
resonant circuit, namely opposite terminals by which the coil 107 and the
capacitor 108 are connected in parallel. The power source circuit 105
having a rectifier circuit, a capacitor and the like converts the AC
power induced in the resonant circuit into DC power.

[0039] Subsequently, the functional unit 106 of the RFID tag is driven
based on the DC power generated in the power source circuit 105. The
selector circuit included in the functional unit 106 controls the
switches 109 and 110 to supply the generated DC power to the display
portion 103a. The aforementioned state is maintained to continuously
generate DC power as long as the parallel resonant circuit is in the
resonant state, thereby the generated DC power is used for driving the
display device 102.

[0040] After that, when the display device 102 having the RFID tag 103b
gets out of the region 201 where the signal 120 from the antenna 104 of
the reader/writer side can be detected (which corresponds to a region
shown by the slant bars in FIG. 2B), the parallel resonant circuit stops
the resonant oscillation, thereby the power source circuit 105 and the
functional unit 106 stop their operations. At this time, the control
terminals of the switches 109 and 110, which have been controlled by the
selector circuit included in the functional unit 106, can be brought into
a floating state. When the RFID tag 103b stops its function, power is
required to be supplied from the battery 111. As a favorable example, it
is preferable to provide such a configuration that when the RFID tag 103b
stops its function, the control terminals of the switches 109 and 110,
namely output terminals of the selector circuit included in the
functional unit 106 are fixed at VSS. Specifically, there is such a
method that a resistor with high resistance is interposed between the
output terminals of the selector circuit included in the functional unit
106 and VSS. Alternatively, there is such a method that VDD used in the
functional unit 106 is set to have the same potential as VSS when the
power supply from the power source circuit 105 is stopped, or the like.
For example, when the functional unit 106 is in operation, the output
terminals of the selector circuit output signals for controlling the
switches 109 and 110, whereas when the functional unit 106 stops its
operation and the output terminals of the selector circuit are brought
into a floating state, the potentials of the output terminals of the
selector circuit included in the functional unit 106 are fixed at VSS by
the aforementioned configuration. When such a state is obtained, it is
only necessary that power be supplied to the display portion 103a from
the battery 111.

[0041] Although the battery 111 is taken as an example of a second power
supply source in addition to the DC power generated by the RFID tag 103b
as a first power supply source in the invention, only the first power
supply source may be used for driving the display device 102. In such a
case, the selector circuit included in the functional unit 106 is not
required, and the portable terminal can be used only in the region where
signals from the antenna 104 of the reader/writer side can be detected.

[0042] Note that the power source circuit 105 included in the RFID tag
103b generates power by detecting signals from the reader/writer, and
this power is preferably large enough to drive the display device 102. In
general, it is considered that in an RFID tag that uses a frequency band
of 13.56 MHz, a power source circuit is required to output power with
about several microwaves to several tens of microwaves for driving a
functional unit provided in the RFID tag. Accordingly, in view of the
characteristic variations of TFTs, conversion efficiency or the like, it
is preferable to use as the display device 102, a light-reflective liquid
crystal display device with relatively small total power consumption.

[0043] Meanwhile, in the case of using as the display device 102, a
light-transmissive liquid crystal display device, a self-luminous display
device using EL (ElectroLuminescence) elements or the like, for example,
the backlight and the EL elements consume relatively big power.
Accordingly, such a configuration may be employed that the power
generated by the aforementioned method is used for driving only a driver
portion of the display device 102 while a fixed power or a battery is
constantly used for supplying power to the backlight or the EL elements.
In such a case, another power supply path that is not via the switches
109 and 110 is required.

[0044] Although this embodiment illustrates one mode of the invention
where a battery is used as a second power supply for driving the display
device, by taking into account that the power source circuit provided in
the RFID tag is not capable of generating very big power, a similar
technique can be applied to the drive of the other components that
constitute the portable terminal.

Embodiment 1

[0045] Description is made with reference to FIG. 3 on a detailed
structure of a display device included in a portable terminal of the
invention. The display device is provided with a pixel portion 302 where
pixels each including a TFT and a display element such as a liquid
crystal element or an EL element are arranged in matrix over an
insulating substrate 301 formed of plastic or the like. On the periphery
of the pixel portion 302, a source driver 303 and a gate driver 304 are
provided to drive each pixel in the pixel portion 302. The pixel portion
302, the source driver 303 and the gate driver 304 belong to the display
portion 103a in FIG. 1. Meanwhile, since an RFID tag 305 has higher
flexibility in circuit designs and shapes as compared to the pixel
portion 302, the source driver 303 and the gate driver 304, it may be
provided in the margin of the substrate 301 that is left after disposing
the aforementioned circuits. Signal input/output to/from these circuits
and power supply from an external power source such as a battery may be
carried out through a flexible printed circuit (FPC) 306.

[0046] In addition, though not shown in FIG. 3, a counter substrate is
attached onto the insulating substrate 301 for sealing the liquid crystal
elements or the EL elements. The counter substrate is required to be
selected in accordance with the elements that constitute the display
portion: if light is required to be extracted from the counter substrate
side, the counter substrate has to be a light-transmissive substrate,
whereas if light is not extracted from the counter substrate side, for
example, in the case of using EL elements of a bottom-emission type in
particular, the counter substrate may be replaced by a metal sealing can.

[0047] In addition, as for a coil and a capacitor for constructing an
antenna of the RFID tag, a coil 401 and a capacitor (not shown) may be
formed over the same insulating substrate 301 as, and concurrently with
the pixel portion 302, the source driver 303, the gate driver 304 and the
RFID tag 305 as shown in FIG. 4A. Note that the size of the coil and the
capacitor differs depending on the resonance frequency. Further, in the
case of constructing the capacitor by forming a thin film over the
insulating substrate, quite a large area is required for obtaining high
capacity. This requirement of areas is the same in the formation of a
coiled wire. Therefore, in the case where an increase in the substrate
area becomes a problem due to the incorporated antenna (specifically, in
the case where a housing of an electronic appliance to which the display
device of the invention is applied is small and a reduction in frame size
is required, for example), the coil 401, a capacitor 402 and the like may
be mounted on another substrate as shown in FIG. 4B so that they are
connected to the RFID tag 305 through the FPC 306.

Embodiment 2

[0048] Description is made with reference to FIGS. 5A to 5C on
applications of the invention. Antennas 502 of readers/writers are built
in a table 501, for example inside a top board of a table 501 set in the
general institution. When a user puts a portable terminal 503 on the
table, an antenna in the portable terminal 503 detects signals outputted
from the antenna 502 of the reader/writer on the table 501, thereby a
power source circuit in the portable terminal 503 is activated. While the
user is using the portable terminal 503 while setting on the chair, a
display device in the portable terminal 503 can be driven by the DC power
generated by the power source circuit in the portable terminal 503.

[0049] Note that when assuming the aforementioned use environment, such
application can be enabled in using a portable terminal at an office for
example, that the personal identification is carried out by using an
identification function as the primary function of the RFID tag,
concurrently with the power supply as described above. Identification
data includes various data such as the control data for access permission
to computer disks at an office, for example, when a user connects his/her
portable terminal to a LAN or the like.

[0050] Meanwhile, when assuming applications of RFID tags to electronic
books, image viewers, music players or the like, it is necessary that a
function of a reader/writer be provided in a portable terminal 511 such
as an electrical book, an image viewer or a music player, while an RFID
tag 513 be incorporated in a receiver 512. As long as the receiver 512 is
in the condition capable of detecting a signal 520 from an antenna of the
reader/writer that is provided in the portable terminal 511 such as an
electrical book, an image viewer or a music player, power for driving the
receiver 512 can be generated in the RFID tag 513 by a similar method of
the invention.

[0051] Further, in the case where multiple users have their respective
receivers 512, and data stored in one portable terminal 511 such as an
electrical book, an image viewer or a music player is to be reproduced as
shown in FIG. 5C, such a configuration may be constructed that individual
identification numbers are assigned to the RFID tags 513 provided in the
respective receivers 512, so that at the time when each ID number is read
out by the reader/writer of the portable terminal 511 such as an
electrical book, an image viewer or a music player, a play list set by
each user is read out, and the reading order of data is changed in
accordance with the play list. Each user can use a preferred content at
his/her disposal from one portable terminal 511 such as an electrical
book, an image viewer or a music player.

[0052] Note that the RFID tag used in the invention is not limited to a
certain type, particularly with respect to the standards of frequency
band. There are various standards for the frequency band such as a low
frequency (125 KHz etc.), high frequency (13.56 MHz etc.), ultra-high
frequency (about 900 MHz etc.) and microwave (2.45 GHz etc.). The
intrinsic effect of the invention will not changed by applying the
invention to any of the aforementioned frequency bands. Since each
frequency band has merits and demerits in the commercial field,
communication distance, directivity and the like, the frequency band may
be selected for each application.

[0053] The present application is based on Japanese Priority application
No. 2005-078191 filed on Mar. 17, 2005 with the Japanese Patent Office,
the entire contents of which are hereby incorporated by reference.